After years of being warned about too much sun on the skin, some people, particularly those in nursing homes and darker skinned people, aren't getting enough.

People with highly pigmented skin need three to four times the sun exposure of those with fair skin for adequate vitamin D levels.

Obtaining sufficient levels of sunlight will also vary depending on where a person lives, the time of day and the season.

For example, the guidelines, which have been approved by the Australian and New Zealand Bone and Mineral Society, suggest that six or seven minutes of sunshine to the face, arms and hands once a day during Summer, outside the middle of the day, is enough for light-skinned Australians.

But in July and August, more than half an hour a day may be necessary in Melbourne, Hobart and Adelaide.

Apart from optimising bone health, Prof Ebeling said vitamin D deficiency was also being researched for its role in a range of other health conditions such as multiple sclerosis, rheumatoid arthritis, type 1 diabetes and some types of cancers, although these studies were not yet definitive.